Isomerization of olefins



Patented Nov. 194D UNITED" STATES PATENT OFFICE V accuses rsonmarzs'no v or onerm's tion of Delaware No Drawing. Application June 5, 1931, Serial No. 146,594. In the Netherlands Juno :1, 1936 Y Claims.

1121s invention relates to the isomerization oi" oletlns, and it relates more particularly to a process for the conversion of normal butenes to isobutene.

The principal objector this invention is to provide a practical and economical process in accordance with which the normal butenes (butene- 1 and butene-2) are converted to the more valuable isobutene.

The process of the invention comprises contacting a normal butene, a mixture of normal butenes or almixture, such as a hydrocarbon mixture, comprising one or both normal. butenes with acatalyst consisting of or comprising a phosphorus oxy-acid at an elevated temperature, preterably equal to at least 250? (2., for a time sumcient to effect substantial isomerization of the normal butene or butenes to isobutene but insuflicient to eiiect substantial polymerization,

90 whereby the normal butene or butenes is/are fin serves as the starting material for the manupractically and economically converted to isobutene in good yields while losses of the butenes due topolymer'ization are substantially obviated.

The process of the present invention is of great technical importance .because in accordance therewith isobutene, which valuable tertiary ole- 1 facture of a wide variety of commercially valuable chemical compounds, can be produced on a technicalscale in a simple, practical and economical manner-from the cheaper, less reactive, more readily available and much less valuable normal butenes.

It is known that the butenes, particularly isobutene, can be contacted with catalysts consisting of or comprising phosphoric acid under such conditions thatthe butenes are polymerized to highermolecular weight hydrocarbons. These polymerization processes are executed under con ditions favorable to polymerization but under such conditions of temperature, pressure and contact time that no isomerization of normal butenes present in the reaction mixture can voccur. The polymerization processes using phosphoric acid catalysts are executed at temperatures in all cases, below 250 (2., and preferably at temperatures below 200' 0.; under superatmospheric pressures preferably as high as from 15 to 20 atmospheres; andwith the butenes in contact with the catalyst under the above enumerated conditions of temperature and pressures for periods of time inall cases greater than ten minutes and preferably in the order of one hour or more. it is seen that prior investiga tors in the art of polymerizing butenes by contact with phosphoric acid catalyst did not discover that normal butenes could be isomerized to isobutene because they worked under conditions at which suchisomerization cannot occur and because it was by no meanspredictable that by der diiferent conditions is isomerized to butene-2 are executed at tem- .the butenes in contact with thephosphoric acid the use of radically diilerent conditions of operation, thatis, temperatures not below about 250 0., pressures not. greater than about 5 atmospheres, and contact times not exceeding about one minute, a normal butene could be converted to isobutene in excellent yield while polymerization of the butenes is substantially obviated. Thus, it is seen that the process of the present invention, which process is drawn to the method of converting a normal. butene to isobutene by isomerization, diners from the polymerization processes-of the prior art, not only in the (litterent products obtained, but in being executed unof temperature, pressure and contact time. 15

It is also known that butene-l can be isomerized to the other species of normal butene, namely butene-2 (CHaCH=CHCl-Ia) by contact with a phosphoric acid-diatomaceous earth catalyst under conditions of temperature, pressure and contact time at which isomerization of the normal butenes to isobutene cannot occur. The processes in accordance with which butene-1 25 peratures below 250 0., under superatmospheric pressures of 7 atmospheres and higher, and with catalyst for periods of time in all cases greater than 83 seconds and preferably in excess oil 200 seconds. Under these conditions, isomerization of thenormal butenes to isobutene cannot occur; the prior investigators. in fact, reporting 100% conversion of butene-1 to butene-2.

The source of the normal butene or mixture of normal butenes used in the execution of our invention is immaterial. Pure butene-1 or pure butene-2, or mixtures thereof, or mixtures of one or both of the normal butenes with one or more saturated or unsaturated hydrocarbons as well as other substantially inert materials may be used as starting material. Thus. it is seen that the invention provides for the utilization of the normal butene-content of commercial hydrocarbon mixtures, particularly-those resulting from the cracking of higher molecular weight hydrocarbons and hydrocarbon mixtures, such as petroleum oils, shale oils, petroleum products, animal oils, vegetable oils, coal, peat,'waxes and the like. Normal butene-containing mixtures resulting from the catalytic dehydrogenation of normal butane and normal butane-containing mixtures are also suitable starting materials. A conveniently-treated normal butene-containing hydrocarbon mixture is the butene-butane fraction which may contain, besides one or bpthnormal butenes, isobutene,.' isobutane and normal butane in varying amounts. Mixtures of the desired oleiins with one or more substantially inert materials as nitrogen, parais 60 fins, water vapor, etc. may be treated without separating the normal butenes therefrom. Substantially pure normal butenes or mixtures thereof may be obtained by effecting dehydration of .5 the straight chain butyl alcohols and other suitable means.

The process is executed in the presence of a catalyst consisting of or comprising a phosphorus oxy acid. Representative phosphorus oxy-acids 10 are orthophosphoric acid(H3PO4) metaphosphoric acid (HPOa), pyrophosphoric acid (HAPQOI), orthophosphorous acid (HaPOa) ,hypophosphorous acid (H3PO2), pyrophosphorous acid (M205), etc. Of the phosphorus oxy-acids, orthophos- 15 phoric acid finds general application on account of its isomerizing ability in the reaction, its cheapness, and itsavailability; it is however to be understood that we may apply any of the other phosphorus oxy-acids alone or in admixture with orthophosphoric acid. Varying concentrations of the phosphorus oxy-acids may be employed from, for example, about 50% to about 100% or such acids containing some free phosphorus oxy-acid anhydrides may be used. The phosphorus 015'- 25 acids may be used as suchor in admixture with substantially inert carrier materials, or in admixture with other active isomerization catalysts or agents such as phosphotungstic acid, phos- 80 phomolybdic acid, etc.

use the phosphorus oxy-acids or mixtures thereof in'substantially solid form, this being accome plished by employing said acids in admixture or incorporated with various solid adsorbent ma- 85 terials. Suitable solid adsorbent materials for our purpose are solid materials of predominately siliceous character such as diatomaceous earth, kieselgul1r,-silica, silica gel and other natural or artificially prepared porous silica materials; 9 aluminum silicate containing materials such as i'uller's earth, clays, bentonite, brick screenings, montmorillonite and the like; carbonaceous ,porous materials as coal, charcoal and the like;

a and other suitable solid adsorbent materials 5 whether natural or prepared.

Such solidphosphoric acid catalysts may be easily and cheaplyprepared by mixing the phosphorus oxy-acidor acids and the solid adsorbent material or materials in the desired proportions,

5o heating (calcining) the resulting mixture up to about 300 0., and grinding and sizing the resultant product to produce catalyst particles of th'edesiredsiz'e. Thecatalystmaybeusedinany convenient particle size. In general, particle 55 sizes of 4 to 20 mesh are preferred. In a solid catalyst prepared as above described. the phosphorus oxy-acid is probably present in a more or less bound condition.

In the execution of the invention, we prefer to amples.

In using the solid phosphorus oxy-acid eat so lysts in the process of this invention, only simple equipment is necessarysuch as a reaction tube or tower in which the solid catalyst is placed, as a packing or filler. Tlietemperature of the catavlyst mass may be controlled by suitable internal to and/or external heating means. The treated materials may or maynot be preheated prior to contact with the heated catalyst at the reaction temperature.

'Iheproce'ssmaybeexecutedwiththenormal 7o butenu in the liquid or in thevapor phase. It

is preferably executed with the butenes in the vapor phase because it is in most casesnot desirable to operate at the high pressures which "would*berequiredto maintain the normal butenes 15 in the liquid phase at temperatures of 250 C. or

higher. Since the use of excessively high pressures results in losses of butenes due to p lymerization'which is favored. by pressure. we prefermospherlc, atmospheric or only moderately eleably execute our isomerization process at subatvated pressures. In general, pressures below about 5 atmospheres are suitable and preferred.

In many cases, particularly when operating with the reactants in the vapor phase, it is advantageous to operate with water vapor in the reaction mixture. The presence of water vapor in the reaction mixture aids in maintaining the catalyst at a practical optimum activity during the operation, perhaps by preventing or inhibiting dehydration of the phosphorus oxy-acid.

The process is executed at temperatures at least equal to about 250 C., and preferably at temperatures in the range of from about 250 C. to 550 C. At temperatures below about 250 C., substantially no isomerization takes place under the conditions of contact time-(not greater than about one. minute) and pressure (not greater than about 5 atmospheres) at which the process is executed. At temperatures greater than about 550 0., losses due to polymerization and cracking are prohibitive. In general, when the contact time is from about 2 to 50 seconds and the process is executed in the vapor phase with a solid phosphoric acid catalyst, excellent results maybe obtained by using temperatures of from 275 C. to 325 C.

In the execution of the process of this inven-" tion, we employ contact times not greater than about one minute, and preferably from about 2 to about 50 seconds. The contact timeis calculated from the macroscopic free space in the catalyst and the rate of feedof the gaseous mixture treated. It is computed by simply'jdividing the macroscopic free space in the catalyst in c. c.

by the gas feed in c. c. per second at the reaction 40 temperature and atmospheric pressure.- vThe re'-' suit is the contact timegin seconds. When using contact times not greater than about one minute,

4 modes of executing the invention. The invention isnottoberegardedasrestrlctedtothemethods and conditions specified in the illustrative ex- Emmple I A Pyrex glass reaction tube having an internal diameter ofabout24 mm. was packedwith granules (4 to 10 mesh) ofa solid catalyst ofa calcined mixtureof commercial orthophosphoric acid and kieselguhr. The packed reaction tube contained an apparent volume of about 100 c. c. orthesolidcatalyst. I

The solid phosphoric acid earth catalystwaspreparedbymixingaboutflparts about 89%) with about 18 by weight 01 by weight of commercial phosphorlcacid (conc.

kieseiguhr. The resultant :mas's at about 250 C. for a'sbort-time and thensr und and sizedtoproduce granules of about 4 tom mesh.

Experiments were made at temperatures of 275 C. and 325 C. and atmospheric pressure at diil'erent contact times. In order to avoid a change in water-content of the catalysts during the operations at the different temperatures. which change in water-content might cause a 75 amass C 3 changeincatalystactivity.theruns etzvs- C.were tures prepared in-accordance with the process or made with the above-described catalyst which the invention are useful for a wide variety of had been previously subjected to a'dehydration l 'i l- T m be used as startinl treatment at about 275 C. under reduced presrials in the production of a wide variety ofusesure for about 24 hours, and those at 325 C. with in! products. For example, the mixture of bu- I a catalyst which had previously beendried under tenes may be treated under such conditions that reduced pressure at 325 0. for about the-sam the isobutene-content thereof is selectively polyperiodof time. merized to diisobutylenc which may then be The contact times in the various runs was calseparated and hydrogenated to iso-octane. If

culated on the macroscopic freespaceinthecatdesired, the butene mixture can be treated un- 10 .alyst. Thisfreespacewasabout 48%.oi' theap- -der such conditions that the isobutene interparent catalyst volume, and was determined by polymerises with the n-butencs to yield higher bringing an apparent volume or 100 c. c. of the molecular weight products which can be hydrocatalyst (which had previously been impregnated senated to valuable motor fuels of high octane with carbon tetrachloride) into a measuring number. The isobutene can be condensed or cylinder havingthesamediameterasthe reaction polymerized with other oleiins asv propene, pentube, and measuring the volmoe of carbon tetratenes, hexenes, etc., parafiins, aromatics, diolechlorlde necessary to fill up the free space in the fins, etc. to yield products useful as motor fuels, impregnated cataylst. resins, lubricating oils, materials for increasing The runs were madewtth a gaseous hydrocarthe viscosity index of'oils, etc. The isobutene bon mixture consistingof about 48.6% by volume may be hydrated to tertiary butyl alcohol, or it of normal butane and about 51.4% by volume or may be chlorinated to isobutenyl chloride, con normal butcnes. verted to isobutyl chloride, etc.

The gaseous mixture leaving the reaction tube While we have described our invention in a dewas passed into a condenser kept at about 10 C. tailed manner and provided specific examples for condensation of any polymers formed. The illustrating suitable modes of executing the total volume, the total olefin content and the same, it is to be understood that modifications isobutene content of the gaseous mixture dismay be made and that no limitations other than charged fromthecondenserwasthen'determined. those imposed by the scope of the appended 80 The results of the runs are slven in the followlaims are intended.

ing table: We claim as our invention:

. 1. A process for the conversion of a normal v oigm mixture butene to isobutenewhich commas contacting Contact nut Pol {the normal butene with a ca t comprising 3 :2: Q, m 5 a phosphorus oxy-acid at a temperature of from g :3 I about 2503 c. to about 550 0. for from 2 to so seconds, whereby substantial conversion of the normal butene to isobutene is eiiected while 1313?: a? :1: at: &: it: polymerization of-the butenes is substantially 40 215.... 5.40 not 14.0 sat on I 13.0 obviated. 1 o

10.00 an as no 0.15 ms 2. A processior the conversion of a normal- Z1: {,3 8:22 3;: butene to isobutene which comprises passing a saoo ass as a: 1.45 4.1 normal butene while in the g'aseousstate into contact at a pressure not greater than about 5 The above data show the influence of the temm sp er it a t t c mp sin ap s- 4s perature and contact time on the conversion .of Phorus XY- oid at a t mp t fr m about the normal butene to isobutene. 250 C. to about 550 C. atsuch a rate that the mm H contact time is from 2 to seconds, whereby v substantial conversion of thenormal butene to so The following nm were made using the same Y isobutene is effected while polymerization of the so catalyst and equipment described in Example I. butenes is substantially obviated. The 11.1118 were made at aboutatmosphericpres- 8. A process for the conversion of a normal sure with a gaseous mixture of normal butenes butene to isobutene which comprises passing a which contained about 3% by volume of 180- normal butene while in the gaseous state into butene- The me mix re; PM er contact at about atmospheric pressure with a as the catalyst together with an equimolecular catalyst comprising a phosphorus oxy-acid at-a. amotmt of water vapor. The results are given temperature of from about 250' c. to about 550?. in the following table: C. at such arate that the contact time is from about 2 to about 50 seconds, whereby substannnt hy drocarbongas tial conversion of the normal butene to isobutene so Contact is eflected while polymerization of the butenes is isobutene, n-Butsne, substantially obviated. v "m by 4. A process for the conversion'of a normal butene to isobutene which comprises contacting Temp v of the mixture is effected while polymerization of The above data show that about 250'- C. is the butenesissubstantially obviated.

about the minimum temperature ,'for practical 6. A process for the conversion of a normal and economical operation of the process. butene to isobutene which comprises passing a Q75 The isobutene or isobutene-containing mixgaseous hydrocarbon mixture containing bu- 75 M m a hydrocarbon mixture containing at least one ass sas no.3 normal butene in substantial amount with a g; a: 3%} catalyst comprising a phosphorus oxy-acid at a 21.0 as 01.5 temperature of from about 250 0. to about 550' g; t 33;; C. for aperiodof 2 to 50 seconds, whereby sub- -2 M M stantial conversion of the normal butenecontent tene-l and butene-2 in substantial amounts into contact at a pressure not greater than about 5 atmospheres, with a catalyst comprising a phosphorus oxy-acid at .a temperature of from about 250 C. to about 550 C. at such a rate that the contact time is from 2 to 50 seconds, whereby the normal butenes are substantially converted to isobutene while polymerization of the butenes is substantially obviated.

6. A process for the conversion of a normalbutene to isobutene which comprises contacting a normal butene with a solid catalyst comprising a phosphorus oxy-acid and a solid adsorbent material at a temperature 01' from about 250 C. to

- whereby substantial conversion of the normal butene to isobutene is effected while polymerization of the butenes is substantially obviated.

8. A process for the conversion of a normal butene to. isobutene which comprises passing a, normal butene while in the gaseous state intocontact at "a pressure not greater than about-5 atmospheres, with I a. solid catalyst comprising a calcined mixture a phosphorus oxy-acid and a solid siliceous material at a temperature or from about 250- C. to about 550 C. at such a rate that that the contact time is from 2 to 50 seconds, whereby substantial conversion. of the normal butene to isobutene is eflected while polymerization of the butenes is substantially obviated.

9. A process for the conversion of a normal butene to isobutene which comprises passing a normal butene while in the'gaseous state into contact .at about atmospheric pressure with a solid catalyst comprising a calcined mixture or a .phosphoric acid and kieselguhr at a temperature or from about 250 C. to about 550 C. at such a rate that the contact time is from about 2 to about 50 seconds, whereby substantial conversion or the normal butene to isobutene is elected .while polymerization of the butenes is substantially obviated: a

10. A process for the conversion 01 normal butenes to isobutene which comprises passing a gaseous hydrocarbon mixture containing about 50% by volume of butane and about 50% by volume of normal butenes into contact at about atmospheric pressure with a solid catalyst comprising a calcined mixture of a phosphorus oxyacid and a solid siliceous material at a temperature of from about 275 C. to about 325 C. at such a rate that the contact time is from about 2 to about 50 seconds, whereby substantial conversion or the normal butenes to isobutene is effected while polymerization of the butenes is substantially obviated.

11. A process for the conversion of n-butenes to iso-butene-which comprises isomerizing said n-butenesby subjecting the same at temperatures of the order 01' 550-750 F. to contact with a cat- .alyst comprising essentially an acid of phosphorous for a time period of the relatively low. order of about 2 to 5 seconds. i

12. A process for the conversion of n-butenes to iso-butene, which comprises isomerizing said n-butenes by subjecting the same at temperatures oi. the order of 550-750 F., substantially atmospheric pressure and times oi. contact of the relatively low order orabout 2 to 5 secs. to contact with a catalyst comprising essentially an acid of phosphorous.

13. A process for converting n-butene to isobutene which comprises contacting the n-butene with an acid of phosphorus at a temperature of from about 250 to 550 C. for a time period and under a pressure such that isomerization of the n-butene proceeds at'a substantially higher rate than butene polymerization.

14. A process for converting n-butene to isobutene which comprises contacting then-butene with solid phosphoric acid catalyst at a tempera ture of from about 250 to 550 C. fora time pesriod and under a pressure such that isomerization of then-butene proceeds at a substantially higher rate than butene polymerization;

15. A process for converting n-butenes into iso-butene which comprises contacting the nbuteneswith solid phosphoric acid catalyst at irom 550-750 FL, approximately atmospheric pressure and for a time period of the relatively low order 01' about 2-5 seconds, whereby isomerization of the n-butenes proceeds at a higher rate than polymerization of the n-butenes.

ADRIANUS JOHANNES VAN PESKI. HERMANUS FRANS JOSEPH LORANG. 

